Method and apparatus for simulating a hybrid system with registered and concurrent nodes

Abstract

A method for performing simulation on a circuit includes simulating registered and concurrent nodes in the circuit. Only concurrent nodes that are associated with a concurrent feedback loop are simulated until outputs of the concurrent nodes that are associated with the concurrent feedback loop reach a steady state.

1. A method for performing simulation on a circuit, comprising:
 simulating registered and concurrent nodes in the circuit; and 
 simulating only concurrent nodes that are associated with a concurrent feedback loop until outputs of the concurrent nodes that are associated with the concurrent feedback loop reach a steady state. 
 
   
   
     2. The method of  claim 1 , further comprising categorizing nodes in the circuit as being registered or concurrent. 
   
   
     3. The method of  claim 1 , further comprising generating an order in which the registered and concurrent nodes are to be simulated. 
   
   
     4. The method of  claim 3 , wherein the order is randomly generated. 
   
   
     5. The method of  claim 3 , wherein the order is generated based on whether the registered and concurrent nodes are associated with the concurrent feedback loop. 
   
   
     6. The method of  claim 3 , wherein the registered and concurrent nodes are ordered in a queue. 
   
   
     7. The method of  claim 1 , wherein simulating registered and concurrent nodes comprises:
 executing registered and concurrent nodes in the circuit that are coupled to registered and concurrent nodes in the system having data available at outputs; 
 determining whether any registered or concurrent nodes have been executed; 
 executing remaining registered and concurrent nodes in the system that are coupled to registered and concurrent nodes in the circuit having data available at outputs in response to determining that registered or concurrent notes have been executed. 
 
   
   
     8. The method of  claim 7 , further comprising:
 taking executed registered and concurrent nodes out of a queue; and 
 placing remaining registered and concurrent nodes above a sentinel in the queue. 
 
   
   
     9. The method of  claim 7 , further comprising determining that the remaining registered and concurrent nodes are associated with the concurrent feedback loop in response to determining that any registered or concurrent notes have not been executed. 
   
   
     10. The method of  claim 1 , further comprising determining that the circuit includes an unstable concurrent feedback loop if the outputs of the registered and concurrent nodes that are associated with the concurrent feedback loop do not reach a steady state after a threshold amount of simulation has been performed. 
   
   
     11. The method of  claim 1 , further comprising simulating registered nodes associated with the concurrent feedback loop. 
   
   
     12. A machine-readable medium having stored thereon sequences of instructions, the sequences of instructions including instructions which, when executed by a processor, causes the processor to perform:
 simulating registered and concurrent nodes in a circuit; and 
 simulating only concurrent nodes that are associated with a concurrent feedback loop until outputs of the concurrent nodes that are associated with the feedback loop reach a steady state. 
 
   
   
     13. The machine-readable medium of  claim 12 , further comprising instructions which when executed by the processor causes the processor to generate an order in which the registered and concurrent nodes are to be simulated. 
   
   
     14. The machine-readable medium of  claim 13 , wherein the order is randomly generated. 
   
   
     15. The machine-readable medium of  claim 13 , wherein the order is generated based on whether the registered and concurrent nodes are associated with the feedback loop. 
   
   
     16. The machine-readable medium of  claim 13 , wherein simulating registered and concurrent nodes comprises:
 executing registered and concurrent nodes in the circuit that are coupled to registered and concurrent nodes in the system having data available at outputs; 
 determining whether any registered or concurrent nodes have been executed; 
 executing remaining registered and concurrent nodes in the circuit that are coupled to registered and concurrent nodes in the circuit having data available at outputs in response to determining that registered or concurrent notes have been executed. 
 
   
   
     17. The machine-readable medium of  claim 16 , further comprising determining that the remaining registered and concurrent nodes are associated with the feedback loop in response to determining that any registered or concurrent notes have not been executed. 
   
   
     18. The machine-readable medium of  claim 12 , further comprising instructions which when executed by the processor causes the processor to simulate registered nodes associated with the concurrent feedback loop. 
   
   
     19. A scheduler, comprising:
 a simulation unit that executes registered and concurrent nodes in a circuit having data available at its inputs; and 
 a node manager that directs the simulation unit to execute only concurrent nodes that are associated with a concurrent feedback loop until outputs of the concurrent nodes that are associated with the concurrent feedback loop reach a steady state. 
 
   
   
     20. The scheduler of  claim 19 , wherein the concurrent nodes that are associated with the concurrent feedback loop are executed using stale data. 
   
   
     21. The scheduler of  claim 19 , further comprising a node classification unit that identifies whether a node is a registered or concurrent node. 
   
   
     22. The scheduler of  claim 19 , further comprising a dependency unit that identifies whether nodes coupled to an input of a node are registered or concurrent. 
   
   
     23. The scheduler of  claim 19 , wherein the simulation unit updates registered nodes associated with the concurrent feedback loop.